This invention relates to protecting optical surfaces within an optical modules and more specifically, to plugging access channels extending into an electro-optical module or device during manufacturing process steps, thereby preventing contamination of or damage to optical surfaces and optical elements during the manufacturing processes.
During an assembly manufacturing process of opto-electronic units or optical devices such as optical fibers, transmit optical sub-assemblies (TOSA""s) and/or receive optical sub-assemblies (ROSA""s), various operations, such as soldering, are required. These operations may include but are not limited to a sequence of one or more solder flux applications, solder paste depositions, solder reflow and washing to remove any previously deposited flux, or any remaining residue of the flux and solder paste.
The soldering steps are generally accomplished by reflow whereby solder paste or another form of solder is deposited at the site where soldering is to occur; next, the entire assembled unit or at least a portion thereof is heated to a temperature at which the solder is rendered molten and caused to reflow between various juxtaposed electrical contacts which are positioned in contact with the solder or solder paste. This solder reflow operation is conventional and well-known to those of ordinary skill in the art. Thus, the solder paste and the flux coact to permit all the solder pads or contacts in the assembly or subassembly not only to be soldered simultaneously but also with a high degree of quality control.
After solder reflow, upon cooling, a portion of the flux previously deposited in significant quantities may remain and must be removed and cleaned. Typically, this flux removal is accomplished by washing with a water bath. Flux composition is selected to be water soluble to enhance the removal of unconsumed flux from regions near soldered electrical joints.
The optical elements contained within the TOSA (transmit optical subassembly) and ROSA (receive optical subassembly), optical fibers and any exposed optical surfaces may be formed of light transmissive materials which are selected not only to optically function as desired but also to withstand the high temperatures encountered in solder reflow.
Optical fibers are normally glass, while other optical elements may be fabricated of clear high temperature plastics. However, heat may slightly affect the unprotected surfaces of the optical elements. Although not directly heat related, some damage to or degradation of the optical elements such as fiber optic ends, may be caused by contact between optical elements and molten solder, flux, flux residue or vapors resulting from the solder reflow operation.
Additionally, the optical surfaces of the devices or lens surfaces similarly may be contaminated, coated with water, or small quantities of water borne flux which may be deposited on the optical surfaces of the optical fibers. This contamination of the surfaces, a result of the wash operation, may alter or degrade the transmission of optical signals through such optical surfaces.
Other sources of contaminants such as dust or other foreign particles also may accumulate on the optical surfaces and adversely affect the transmission of signals through the optical fibers or other optical surfaces of the optical components during other manufacturing steps or subsequent handling, packaging, shipping or further assembly into larger units or subassemblies. With the optical elements recessed within an optical assembly, the cleaning and/or removal of the contaminants on optical elements and especially the exposed optical surfaces thereof is difficult if not impractical.
It is an object of the invention to protect the optical elements of an optical subassembly at least during the manufacture and assembly of the optical subassembly.
It is another object of the invention to seal the access channel to optical surfaces within an optical subassembly during the manufacturing steps of assembly of the optical subassemblies.
It is a further object of the invention to prevent invasion of water or other contaminants into the region of the optical elements of an optical subassembly during wash operations of the assembly process.
It is an additional object of the invention to withstand temperatures of solder reflow operations during the manufacture of optical subassemblies.
It is still another object of the invention to prevent heat related deformation of the optical subassembly connector by the presence of the invention during solder reflow operations.
It is a still further object of the invention to maintain a continuous seal with the optical subassembly connector housing during all periods for which the invention is resident within the optical subassembly connector housing.
It is a still additional object of the invention to be readily removable from the housing of the optical subassembly.
A channel within the optical subassembly, module housing or connector with optical elements therein. is plugged and sealed in order to seal access to and protect optical components, and particularly the optical surfaces of optical components of an optical subassembly during the manufacturing process steps of assembly of the optical subassembly, and especially the solder reflow and wash steps of such a process. The portions requiring isolation and protection are the exposed optical surfaces of the optical elements.
The channel plug, a fluoro-elastomeric material, is typically by manufactured molding. The fluoro-elastomer is chosen to be capable of withstanding temperatures up to about 260xc2x0 C., the upper limit of a common solder reflow temperature range.
The plug is formed with a plugging and sealing end which is relatively thin but which is sufficiently thick to provide sufficient stability to form a wiping engagement with the walls of a channel within the optical subassembly. The plugging end is molded to form a periphery conforming in shape to the interior of an optical subassembly channel and dimensioned to be slightly larger than the interior of an optical subassembly channel. The peripheral shape of a plug end is substantially the same as but slightly larger than the interior dimensions of sidewalls of the channel to be plugged. Edges of a plugging portion engage the side walls and may be formed either as arcuate edges wherein interior side walls of the channel are similarly arcuate. The top and bottom wall engaging edges may be substantially straight or curved as required to conform to the edges of a cross-section of the channel.
Due to the slightly oversize relationship of the plug end portion to the interior of the channel, the plug deforms, compresses, and/or deflects due to its elastomeric nature, whenever inserted into the channel. The deflection of the edge margins of the plug creates not only a wiping contact and a forceful seal between the edge margins but also an inherent retention force which seals and retains the plug in place until removed by forcible withdrawal. The edge margins similarly will deform or deflect under the withdrawal force being exerted on the plugging end.
In an attempt to restore to its undeformed and undeflected state, the plugging portion exerts a small but sufficient force on the interior of the channel walls to effect a water-tight and debris-tight seal between the plugging portion and the channel walls.
A stem is joined to and extends from one surface of the plug member. The stem terminates in an enlarged flattened bulbous portion configured to be easily and reliably grasped by a thumb and finger in order to pull and remove the plug from the channel of an optical subassembly. The junction between a stem and the sealing plug portion is enlarged in cross-section so that only a narrow peripheral zone or margin of the sealing plug is unsupported by a stem, thereby concentrating deflection of the elastomeric plug member in the periphery or edge margins of the plug portion. This concentration of deflection increases the sealing forces relative to members without similar support.
The opposing face of the plug portion may be provided with protrusions or standoff members to insure that the surface of the plug portion is prevented from contacting the ends of the optical fibers or other optical surfaces within the connector. The standoffs are spaced from each other to provide a space adjacent the ends of the optical fibers or surfaces of the optical components whenever the plug is installed as intended.
This Summary of the Invention is provided to give one of skill in the art a synopsis of the main aspects of the invention and is not intended for limiting nor should it be used to limit the scope of the invention in any manner.
One of skill in the art may acquire a more complete understanding of the invention from the following Detailed Description of the Invention and the attached drawings.